As shown in FIG. 1, the compressor section 10 of a turbine engine can be housed within a compressor outer casing, cylinder or shell 12. The casing 12 can be made of two semi-cylindrical halves secured together at a joint 14, known as the horizontal joint 14 because of its substantially horizontal orientation when assembled. The outer casing 12 encloses a rotor (not shown) on which multiple rows of airfoils or blades 16 are mounted. The rows of blades 16 alternate with the rows of stationary airfoils or vanes 18, which can be attached to and extend radially inward from the compressor shell 12. In some instances, the vanes 18 can be provided in the form of a diaphragm 20. Each diaphragm 20 can include inner and outer radial bands 22,24, referred to as shrouds, with a plurality of vanes 18 circumferentially arrayed therebetween. Like the compressor shell 12, the diaphragm 20 can be made of two substantially semi-circular halves.
The diaphragm 20 can be secured to the compressor shell 12 in various ways. For example, as is known in the art, the compressor shell 12 can include a circumferential slot 26 along its inner peripheral surface 28 for receiving the outer shroud 24 so as to mount the diaphragm 20 on the shell 12. Thus, each half of the compressor shell 12 can hold a substantially semi-circular diaphragm 20. Typically, the outer shroud 24 can fit loosely within the slot 26, as shown in FIG. 2. This loose fit allows relative movement between the diaphragm 20 and the cylinder 12, which can occur when subjected to vibration and other forces during compressor operation. However, over time, this relative movement can lead to wear on the interfacing surfaces of these parts. One area of particular concern is at or near the horizontal joint 14 because the largest relative motion occurs at the free ends of the diaphragm 20. Experience has shown that cracks can develop in the outer shroud 24 at or near the horizontal joint 14 as well as in the inner shroud 22.
There have been prior attempts to reduce the relative movement between these parts and thereby slow the resulting wear. For instance, one approach involves filling the space between the outer shroud and the slot with a packing material, such as a flexible filler. However, the packing material merely fills the gap without exerting any force on the outer shroud of the diaphragm. Eventually, the filler material will wear away.
Another previous system includes the use of cam-type mechanisms. While the cam-type devices can apply an axial load on the shroud, the load is applied at some distance from the horizontal joint 14. Therefore, the cam-type system fails to address the large relative movement near the horizontal joint 14. Further, the cam-type devices are installed through a radial penetration in the compressor cylinder, which presents the additional challenge of sealing such a penetration.
Thus, there is a need for a system for reducing the play between and, ultimately, the wearing of the compressor diaphragm and the compressor cylinder. Ideally, such a system would avoid penetration of the compressor cylinder. In addition, the system should address the known problem areas at or near the horizontal joint.